class Solution {
 public:
  int numWaterBottles(int numBottles, int numExchange) {
    int sum = 0;
    int emptybottles = numBottles;
    while (numBottles != 0) {
      sum += numBottles;
      numBottles = emptybottles / numExchange;
      emptybottles = emptybottles - numBottles * numExchange + numBottles;
    }
    return sum;
  }
};
